The present invention relates to an endoscope for inspecting interior constructions and structures of various organs of human beings, industrial products, etc., and more particularly to an endoscope comprising an image guide bundle, a solid state image sensing device and a monitor for displaying interior structure images having a high image quality.
FIG. 1 shows a typical known endoscope with a monitor comprising a protection tube 1 in which an image guide bundle having a plurality of optical fibers is inserted, a main body 2 to which a television camera 3 supported by a balancer 4 and a stay 5 is secured, and a monitor 6. For instance, the tube 1 is inserted into a stomach through an esophagus and an image of an inner wall of the stomach may be displayed on the monitor 6. In such an endoscope since there are usually broken optical fibers in the image guide bundle, dead spots, i.e. black dots appear in the image displayed on the monitor 6 and thus, the image quality is decreased to a great extent. Usually the image guide bundle includes about forty thousands optical fibers each having a diameter of about 5 .mu.m and arranged regularly. Therefore, in practice, it is not possible to eliminate an occurrence of broken fibers during a manufacturing stage thereof. If the image transferred through the image guide bundle including such broken fibers which can not transfer or transmit light rays is picked up by the TV camera 3 and is displayed on the monitor 6, black dead spots appear in the displayed image and a quality of the image is deteriorated. It should be further noted that broken fibers are produced not only during the manufacturing process, but also during actual usages of the endoscope.
Moreover since the TV camera 3 arranged in front of a light emitting side of the image guide bundle has a higher resolution as compared with a fiber pitch thereof, portions which can not transfer light rays are formed on boundaries between respective fibers each having usually a hexagonal shape due to clads, so that a so called mesh defect is generated in the display image. In this manner, the quality of the image displayed on the monitor 6 is further made lower.